Explosive compositions containing static-proofing ingredient



United States Patent O 3,281,292 EXPLOSIVE COMPOSITIONS CONTAINING STATIC-PROOFING INGREDIENT Errol Linton Falconer, George Whitlock Graham, and Robert Franklin Knott, all of St. Hilaire, Quebec, Canada, assignors to Canadian Industries Limited, Montreal, Quebec, Canada, a corporation of Canada No Drawing. Filed May 15, 1964, Ser. No. 367,873 Claims priority, application Canada, June 4, 1963, 877,190 15 Claims. (Cl. 149-38) This invention relates to explosive compositions comprising ammonium nitrate and a fuel or sensitizer and which are resistant to the development of charges of static electricity.

Explosives composed of ammonium nitrate and oleaginous fuel of the fuel oil type are commonly known in the trade as ammonium nitrate-fuel oil explosives, or simply as AN/F explosives. Those of the AN/FO explosives which contain as an additional fuel or sensitizer particulate aluminumor magnesium or alloy thereof are generally referred to as AN/OF/metal explosives. These explosives are at present widely used in both the construction and mining industries.

Originally employed in surface blasting operations such as in quarrying, open pit mining and the like, these types of explosives have now been introduced into underground mining operations, which application has required new methods of loading the explosives into boreholes. Whereas in surface blasting operations, the boreholes are normally wide diameter vertical holes into which the explosives can be introduced by gravity methods, the boreholes used in underground mining operations may be horizontal or may be driven into the roof of the working area. Because of the granular and free-flowing consistency of AN/FO and AN/FO/metal explosives, it has been necessary to develop means of forcibly injecting the explosives into the boreholes.

An apparatus now commonly exployed for this purpose is a pneumatically operated eductor which discharges the AN/FO or AN/ FO/ metal mixtures into the boreholes through a tube or hose. However, when the explosive mixtures pass through the educator and those, large charges of static electricty are developed. These electrical charges have been measured and in laboratorysimulated borehole loading conditions, charges over 20,000 volts have been recorded. This static electricity causes discomfort to persons operating the eductor loading apparatus and constitutes a continuing hazard in an area where explosives are present. Such charges are capable of detonating electric blasting caps prematurely. Furthermore, they have been shown to be conductible along a length of ordinary safety fuse and are of sufiicient intensity to detonate an ordinary blasting cap attached thereto.

The use or presence of electric blasting caps in areas where AN/FO or AN/FO/metal explosives are in use has been strongly discouraged and has, in fact, in many jurisdictions, been prohibited.

It is an object of the present invention to provide a sensitized ammonium nitrate explosive composition which is resistant to the development of charges of static electri-city. Another object of the invention is to provide a sensitized ammonium nitrate explosive composition which, when employed in a pneumatic borehole loading machine, will not develop hazardous charges of static electricity. Additional objects of the invention will appear hereinafter.

The static-resistant explosive of this invention comprises ammonium nitrate, an oleaginous fuel and, optionally, a particulate light metal, and at least one additive selected from the group consisting of quaternary ammonium salts containing at least one long chain alkyl radical, long chain alkyl pyridinium salts, polyoxyethylene nonyl phenols, polyoxyethylene di-nonyl phenols and polyoxyethylene sorbitan monoesters of long chain .aliphatic acids, the additive being responsible for the static resisatnce of the explosive.

The ammonium nitrate ingredient is usually in the form of prills but other physical forms capable of retaining the oleaginous fuel are suitable. It may be modified by small amounts of materials which impart anti-setting or water-proofing properties. Examples of such materials are kieselguhr, kaolinite, the sodium salt of a mixture of methyl .and dimethyl naphthalene, sulphonic acids and calcium stearate. The ammonium nitrate is suitably present in a concentration ranging from 60 to 98% by weight of the composition. It is, in some cases, advantageous to replace some, suitably up to 35% of the ammonium nitrate by sodium nitrate.

The oleaginous fuel ingredient of the explosive composition is preferably diesel oil or fuel oil but other suitable fuels may be used such as low melting petroleum greases and waxes and partially nitrated derivatives of benzene, toluene, xylene and naphthalene. With petroleum hydrocarbons, maximum blasting efficiency results with amounts of from 2 to 20% of fuel, by weight of the composition.

The optional particulate light metal ingredient is preferably aluminium or an alloy of aluminum, but magnesium, alloys of magnesium, silicon, ferrosilicon and boron may be used although the latter may prove to be more ex pensive, less effective or more difiicult to employ from a production and safety viewpoint than aluminum or aluminum alloys. The particulate metals, when used, may suitably range in particle size from a fine dust to a form not coarser than that which will pass through a size 10 Tyler mesh screen. The aluminum or aluminum alloy is suitably present in a concentration ranging from 1 to 25% by weight of the composition.

As previously mentioned, the static-proofing ingredient of the composition may be any one or a combination of:

(a) quaternary ammonium salts containing :at least one long chain alkyl radical, i.e. an alkyl radical having from 12 to 18 carbon atoms, and analogous pyridinium salts;

(b) polyoxyethylene nonyl phenols having the chemical formula:

o n-O(OCHzCI-I1)DOH the value of n varying between 3 and 9;

(c) polyoxyethylene di-nonyl phenols having the chemical formula:

(oomounnou the value of n varying between 6 and 18; and

(d) polyoxyethylene sorbitan monoesters of long chain aliphatic acids, i.e. esters which are liquid at 25 C. and are derived from aliphatic acids having from 12 to 18 carbon atoms.

The static-proofing ingredient is preferably used in a concentration of from 0.1 to 5% by weight of the composition.

It has been surprisingly found that many so-called autistatic agents commonly employed in the textile, plastics and other industries to reduce static accumulation are not effective static proofing ingredients in AN/FO and AN/FO/metal explosives. Many of these well known anti-static agents produce little or no change in the staticgenerating tendency of AN/FO and AN/FO/metal mixfinely divided aluminum metal (99% pure). of mixtures were made up from this composition by add tures while others have been found to increase the quantity of static electrical build-up in pneumatically loaded explosives. Particularly, it has been found also that the use of some well known anti-static agents in these explosives contribute significantly to the setting-up or caking of the explosives under conditions of normal storage, thus making the explosives unsuitable for use.

The explosive composition of this invention is conven iently and simply prepared by dispersing the static-proofing agent in the oleaginous fuel and adding the dispersion to the ammonium nitrate, which may be coated with an anti-setting and/ or moisture proofing agent.

Where it is desired to employ a particulate light metal as a sensitizer in addition to the oleaginous fuel, the ammonium nitrate and metal may first be blended together, the oleaginous fuel being then added after dispersion in the static-proofing agent.

The static-resistant explosive composition of this invention may be prepared in any suitable type of mixing equipment which is adequately grounded to earth. Preferably, the mixer should have no rapidly moving parts and have a tumbling action combined with a lifting of the material from the bottom of the mixer to the top to ensure intimate blending. The conventional ribbon type or rotating plough type mixers are suitable for this purpose.

As previously mentioned, these compositions have potential uses in blasting operations where the explosive is forced into the borehole through a tube or hose, thus introducing the .hazard of building up electrical charges on the hose and the explosive. They are likely to be most useful in underground blasting operations although they will be useful also in surface blasting as electrical charges may be produced through the tumbling action of the composition in gravity loading of vertical boreholes.

I The invention is further illustrated but not limited by the following examples in which parts and percentages are by weight unless otherwise stated.

Example I An ammonium nitrate-fuel oil blasting composition was prepared by mixing 94 parts of ammonium nitrate prills and 6 parts of diesel oil. A series of mixtures were made up fromthis composition by adding definite percentages of the materials shown in Table I and three poundsof each mixture were then loaded 'by a pneumatic eductor into a glass pipe to simulate dry borehole conditions. A conductive probe, inserted through a rubber stopper in the end of the pipe was connected through a micrometer to ground, the static electricity leaking from the charge through the meter. The results are given in Table I.

The percentage of static electricity was calculated. on the basis of 100% for the ammonium nitrate-fuel oil mixture without additive.

Example 2 An ammonium nitrate-fuel oil-aluminum blasting composition was prepared by mixing 87.1 parts of ammonium nitrate prills, 2.4 parts of diesel oil and 10.0 parts of A series ing definite percentages of the materials shown in Table II- 1. 62% atN prills, 20% sodium nitrate, 10% aluminum, 8%

Three pounds of each mixture were then loaded by pneumatic eductor and the percent static electricity generated was measured as in Example 1. The results are given in The percentage of static electricity was calculated on the basis of for the ammonium nitrate-fuel oilaluminum mixture without additive.

Example 3 An ammonium nitrate-sodium nitrate-dinitrotoluenealuminum blasting composition was prepared by mixing 62 parts of ammonium nitrate prills, 20 parts of sodium nitrate, 10 parts of finely divided aluminum (99% pure) and 8 parts of dinitrotoluene. A separate similar composition was made up and 2% by weight of polyoxyethylene sorbitan monolaurate was added. Three pounds of each composition were then loaded by pneumatic eductor and the static electricity generated was measured as in Example 1. The results are given in Table III.

TABLE III Percent Composition tatic Electricity dm 1 0 lane 2. 60% AN prills, 20% sodium nitrate, 10% aluminum, 8%

dinitrotoluene, 2% polyoxyethylene sorbitan monolaurate. 15

On the basis of 100% static electricity for the composition without additive, the composition containing the additive was calculated to generate 15% static electricity.

Example 4 An ammonium nitrate-fuel oil blasting composition was prepared by the method described in Example 1 and three mixtures were prepared, each containing .l% of a. well known anti-static agent. The mixtures were then loaded pneumatically as in Example 1 and the static electricity measured. In Table IV the results are expressed on the basis of 100% for the ammonium nitrate-fuel oil mixture without additive.

TABLE IV Percent Additive Static Electricity 1. None 100 3. .1% iso ropylamide oi dodecyl benzene sulphonic acid---" 421 3. .l% sor itan monomlmimrs 204 4. .l% polyoxyethyleue (3.6) tridecyl alcohol chain alkyl radical, long chain alkyl pyridinium salts,

polyoxyethylene nonyl phenols, polyoxyethylene di-nonyl phenols and polyoxyethylene sorbitan monoesters of long chain aliphatic acids.

2. An explosive composition as claimed in claim 1 wherein sodium nitrate is substituted for part of the ammonium nitrate.

3. An explosive composition as claimed in claim 1 wherein a member selected from the group consisting of finely divided aluminum and alloys thereof is substituted for part of the ammonium nitrate.

4. An explosive composition resistant to the development of charges of static electricity comprising from 60 to 98% by weight of ammonium nitrate, from 2% to 20% by weight of an ole-aginous fuel selected from the group consisting of liquid petroleum hydrocarbons, low melting petroleum greases and waves and partially nitrated derivatives of benzene, toluene, xylene and naphthalene and from 0.1% to 5% by weight of at least one additive selected from the group consisting of quaternary ammonium salts containing at least one long chain alkyl radical, long chain alkyl pyridinium salts, polyoxyethylene nonyl phenols, polyoxyethylene di-nonyl phenols and polyoxyethylene sorbitan monoesters of long chain aliphatic acids.

5. An explosive composition resistant to the development of charges of static electricity comprising from 30% to 96% by weight of ammonium nitrate, from 1% to 25% by Weight of a member selected from the group consisting of finely divided aluminum and alloys thereof, from 2% to 15% by weight of an oleaginous fuel selccted from the group consisting of liquid petroleum hydrocarbons, low melting petroleum greases and waxes and partially nitrated derivatives of benzene, toluene, xylene and naphthalene from to 35% by Weight of sodium nitrate, and from 0.1% to by weight of at least one additive selected from the group consisting of quaternary ammonium salts containing at least one long chain alkyl radical, long chain alkyl pyridinium salts, polyoxyethylene nonyl phenols, polyoxyethylene di-nonyl phenols and polyoxyethylene sorbitan monoesters of long chain aliphatic acids.

6. An explosive composition as claimed in claim 1 wherein the quaternary ammonium salts contain at least one long chain alkyl radical having from 12 to 18 carbon atoms.

7. An explosive composition as claimed in claim 4 wherein the quaternary ammonium salts contain at least one long chain alkyl radical having from 12 to 18 carbon atoms.

8. An explosive composition as claimed in claim 1 wherein the polyoxyethylene nonyl phenols have the forthe value of n varying between 3 and 9.

9. An explosive composition as claimed in claim 4 wherein the polyoxyethylene nonyl phenols have the formula:

ofiw-oaoornonmon the value of n varying between 3 and 9.

10. An explosive composition as claimed in claim 1 wherein the polyoxyethylene di-nonyl phenols have the formula:

gi oomormnon o in CoHts (OCHzCH2)nOH the value of n varying between 6 and 18.

12. An explosive composition as claimed in claim 1 wherein the polyoxyethylene sorbitan monoesters of long chain aliphatic acid monoesters are liquid at 25 C. and are derived from aliphatic acids having from 12 to 18 carbon atoms.

13. An explosive composition as claimed in claim 4 wherein the polyoxyethylene sorbitan monoesters of long chain aliphatic acid monoesters are liquid at 25 C. and are derived from aliphatic acids having from 12 to' 18 carbon atoms.

14. An explosive composition as claimed in claim 1 wherein the ammonium nitrate is pre-treated with a member selected from the group consisting of anti-setting and water-proofing agents.

15. An explosive composition as claimed in claim 3 wherein the aluminum ingredient has a particle size not greater than 10 standard Tyler mesh size.

References Cited by the Examiner UNITED STATES PATENTS 2,719,153 9/1955 Schulz ..1492

BENJAMIN R. PADGETT, Primary Examiner.

S. I. LECHERT, JR., Assistant Examiner. 

1. AN EXPLOSIVE COMPOSITION RESISTANT TO THE DEVELOPMENT OF CHARGES OF STATIC ELECTRICITY COMPRISING AMMONIUM NITRATE, AN OLEAGINOUS FUEL SELECTED FROM THE GROUP CONSISTING OF LIQUID PETROLEUM HYDROCARBONS, LOW MELTING PETROLEUM GREASES AND WAXES AND PARTIALLY NITRATED DERIVATIVES OF BENZENE, TOLUENE, XYLENE AND NAPHTHYLENE AND AT LEAST ONE ADDITIVE SELECTED FROM THE GROUP CONSISTING OF QUATERNARY AMMONIUM SALTS CONTAINING AT LEAST ONE LONG CHAIN ALKYL RADICAL, LONG CHAIN ALKYL PYRIDINIUM SALTS, POLYOXYETHYLENE NONYL PHENOLS,POLYOXYETHYLENE DI-NONYL PHENOLS AND POLYOXYETHYLENE SORBITAN MONOESTERS OF LONG CHAIN ALIPHATIC ACIDS.
 3. AN EXPLOSSIVE COMPOSITION AS CLAIMED IN CLAIM 1 WHEREIN A MEMBER SELECTED FROM THE GROUP CONSISTING OF FINELY DIVIDED ALUMINUM AND ALLOYS THEREOF IS SUBSTITUTED FOR PART OF THE AMMONIUM NITRATE. 